Perfluorinated polyether compounds having a plurality of functional groups at their terminals are widely used as a lubricant, a surface modifier, a surfactant, etc. The present inventors have provided an effective process for producing a compound containing no —OCF2O— structure among perfluorinated polyether compounds (Patent Document 1). Further, they have found that such a compound is excellent in self-replenishing property and is chemically stable. The self-replenishing property is such a nature that when a part of a coating film formed by application of a compound to a substrate surface becomes defective by a certain reason, the compound around the defective portion will cover the defective portion to replenish the defective portion.
However, they have noticed that when the compound containing no —OCF2O— structure is applied to a substrate, the viscosity tends to be high as compared with a perfluoropolyether having a molecular weight at the same level and containing a —OCF2O— structure. They have noticed that particularly the viscosity of a polyether containing no —OCF2O— structure and having three or more hydroxyl groups at its terminal is higher by several times. Further, when a polyether compound containing no —OCF2O— structure is used at low temperature, the self-replenishing property tends to decrease.
Patent Document 1: WO04/035656